Phase-change material-based switch

Abstract

Phase-Change Material-Based Switch This description relates to a phase-change material-based switch (200) comprising: – a region (103) of said phase-change material connecting the first and second conduction electrodes (101A, 101B) of the switch; and – a polarization rotator (205) for a laser signal to activate the switch, located opposite a face of the region of said phase-change material. Figure for the abbreviation: Fig. 2B

Description

Title of the invention: Switch based on phase change material Technical field

[0001] The present description relates generally to electronic devices. The present description relates more particularly to switches based on a phase change material, capable of alternating between a crystalline, electrically conductive phase and an amorphous, electrically insulating phase. Prior art

[0002] Various applications take advantage of switches, or interrupters, based on a phase-change material to allow or prevent the flow of an electric current in a circuit. Such switches can in particular be implemented in radiofrequency communication applications, for example to switch an antenna between transmission and reception modes, activate a filter corresponding to a frequency band, etc.

[0003] Existing phase change material based switches, however, suffer from various drawbacks. Summary of the invention

[0004] There is a need to improve existing phase change material based switches.

[0005] For this, one embodiment provides a switch based on a phase change material comprising: - a region of said phase change material connecting first and second conduction electrodes of the switch; and - a polarization rotator of a laser signal for activating the switch, located opposite a face of the region made of said phase-change material.

[0006] According to one embodiment, the polarization rotator comprises a central region made of a first material surrounded by a peripheral region made of a second material with an optical index lower than that of the first material.

[0007] According to one embodiment, the polarization rotator is adapted to cause, between an input face and an output face, opposite the input face, a rotation of polarization of the laser signal activating the switch between a transverse electric mode and a transverse magnetic mode.

[0008] According to one embodiment, the central region has, along a direction of propagation of the laser signal in the polarization rotator, a section of asymmetric shape.

[0009] According to one embodiment, the section of the central region is invariable over the entire length of the polarization rotator.

[0010] According to one embodiment, the section of the central region has, in a plane orthogonal to the direction of propagation of the laser signal, an L shape.

[0011] According to one embodiment, the section of the central region varies along a propagation direction of the laser signal in the polarization rotator.

[0012] According to one embodiment, the first and second conduction electrodes are part of an antenna element of a transmitting array cell or reflecting array cell.

[0013] One embodiment provides a transmitter array or reflector array cell comprising at least one switch as described.

[0014] One embodiment provides a transmitter network or a reflector network comprising: - a plurality of cells as described; - one or more laser sources; and - a control circuit for the laser source(s).

[0015] According to one embodiment, each laser source is part of the same chip as each switch with which it is associated.

[0016] One embodiment provides an antenna comprising a transmitting array or a reflecting array as described and at least one source configured to irradiate one face of the array. Brief description of the drawings

[0017] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0018] [Fig.lA] and [Fig.lB] are schematic and partial views, respectively from above and in section along plane BB of [Fig.lA], illustrating an example of a switch based on a phase change material;

[0019] [Fig.2A] and [Fig.2B] are schematic and partial views, respectively from above and in section along plane BB of [Fig.2A], illustrating an example of a switch based on a phase change material according to one embodiment;

[0020] [Fig.3] is an isometric, schematic and partial view illustrating an example of a switch based on a phase change material according to one embodiment;

[0021] [Fig. 4] is a schematic and partial side view of an example of a transmitting array antenna of the type to which, by way of example, the described embodiments apply; and

[0022] [Fig. 5] is an isometric, schematic and partial view of an elementary cell of the transmitting network of the antenna of [Fig. 4] according to one embodiment. Description of the embodiments

[0023] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0024] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the control circuits of the switches based on a phase-change material and the applications in which such switches may be provided have not been detailed, the described embodiments and variants being compatible with the control circuits of the usual phase-change material switches and with the usual applications implementing switches based on a phase-change material.

[0025] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0026] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0027] Unless otherwise specified, the expressions “about”, “approximately”, “substantially”, and “of the order of” mean to within 10%, preferably to within 5%.

[0028] [Fig.lA] and [Fig.lB] are schematic and partial views, respectively from above and in section along the plane BB of [Fig.lA], illustrating an example of a switch 100 based on a phase change material. In the illustrated example, the plane BB of [Fig.lA] is a vertical plane parallel to a conduction direction of the switch 100.

[0029] In Figures 1A and 1B, the conduction direction of the switch 100 is parallel to a horizontal axis Oy, and the plane BB is parallel to a vertical plane Oyz orthogonal to an axis Ox.

[0030] In the example shown, the switch 100 comprises electrodes of conduction 101A and 101B. The conduction electrodes 101A and 101B of the switch 100 are for example intended to be connected to a radiofrequency communication circuit, not detailed in the figures. The conduction electrodes 101A and 101B are made of an electrically conductive material, for example a metal, for example copper or aluminum, or a metal alloy. Furthermore, the conduction electrodes 101A and 101B may have a single-layer or multi-layer structure.

[0031] Although this has not been detailed in figures 1A and 1B in order not to overload the drawing, the conduction electrodes 101A and 101B of the switch 100 are for example located on and in contact with an upper face of an electrically insulating layer, for example made of silicon dioxide (SiO2), coating a substrate. By way of example, the substrate is in this case a wafer or a piece of wafer made of a semiconductor material, for example silicon.

[0032] In the example illustrated, the switch 100 further comprises a region 103 made of a phase-change material connecting the conduction electrodes 101A and 101B. Although this has not been detailed in the figures, the region 103 made of phase-change material covers, for example, an upper face of another electrically insulating layer, for example made of silicon dioxide, extending laterally between the electrodes 101A and 101B, the electrically insulating layer being flush, for example, with the upper faces of the electrodes 101A and 101B. In the example shown, the region 103 made of phase-change material extends onto and in contact with a portion of the upper face of each conduction electrode 101A, 101B. By way of example, the region 103 made of phase-change material has a thickness of the order of 100 nm.

[0033] For example, region 103 of switch 100 is made of a so-called “chalcogenide” material, i.e. a material or alloy comprising at least one chalcogen element, for example a material from the family of germanium telluride (GeTe), antimony telluride (SbTe) or germanium-antimony-tellurium (GeSbTe, commonly referred to by the acronym “GST”). As a variant, region 103 is made of vanadium dioxide (VO2).

[0034] Generally speaking, phase change materials are materials capable of alternating, under the effect of a temperature variation, between a crystalline phase and an amorphous phase, the amorphous phase having an electrical resistance greater than that of the crystalline phase. In the case of the switch 100, this phenomenon is used to obtain a blocked state, preventing the flow of a current between the conduction electrodes 101A and 101B, when the material of the region 103 located between the conduction electrodes is in the amorphous phase, and an on state, allowing the flow of current between the conduction electrodes 101A and 101B, when the material in region 103 is in the crystalline phase.

[0035] In the example shown, the switch 100 further comprises a waveguide 105 located opposite the region 103 made of phase-change material and extending laterally along a main direction substantially orthogonal to the conduction direction of the switch 100. In FIGS. 1A and 1B, the waveguide 105 of the switch 100 extends parallel to the axis Ox. The waveguide 105 comprises, for example, a first end located opposite an upper face of the region 103 made of phase-change material and a second end, opposite the first end, intended to be illuminated by a laser source LS. By way of example, the radiation emitted by the laser source LS has a transverse magnetic polarization (TM) or a transverse electric polarization (TE).

[0036] In the illustrated example, the waveguide 105 comprises a central region 107, or core, surrounded by an electrically insulating peripheral region 109. In the illustrated example, the central region 107 of the waveguide 105 extends parallel to the axis Ox. The central region 107 and the peripheral region 109 of the waveguide 105 are made of materials chosen so as to obtain a contrast of optical indices making it possible to confine and guide an optical mode of interest emitted by the laser source LS. The material of the central region 107 of the waveguide 105 has, for example, an optical index higher than that of the peripheral region 109. For example, the central region 107 of the waveguide 105 is made of silicon nitride and the peripheral region 109 is made of silicon dioxide.

[0037] The plane BB of [Fig. 1A] is substantially orthogonal to a direction of propagation of the laser radiation in the waveguide 105. The direction of propagation of the laser radiation in the waveguide 105 is, in the example illustrated, parallel to the axis Ox. In the example shown, the peripheral region 109 of the waveguide 105 covers the faces of the central region 107 parallel to the direction of propagation of the laser radiation (the lateral, lower and upper faces of the central region 107 of the waveguide 105 parallel to the axis Ox, in FIGS. 1A and 1B). In this example, a portion of the peripheral region 109 of the waveguide 105 extends vertically, along the vertical axis Oz orthogonal to the horizontal axes Ox and Oy, from a face of the central region 107 located opposite the region 103 of phase change material (the lower face of the central region 107 of the waveguide 105, in the orientation of [Fig.lB]) to a face of the phase change material region 103 opposite the conduction electrodes 101A and 101B (the upper face of the phase change material region 103, in the orientation of [Fig.lB]).

[0038] In the example shown, the central region 107 presents, in sectional view along the plane BB orthogonal to the direction of propagation of the laser radiation in the guide waveguide 105, a section of substantially rectangular shape. For example, the central region 107 has, in sectional view along the plane BB, a width w (along the axis Ox) equal to approximately 300 nm and a height h (along the axis Oz) equal to approximately 350 nm. Furthermore, the central region 107 of the waveguide 105 is separated from the region 103 of phase change material by a distance g. In this example, the distance g is equivalent to a thickness of the part of the peripheral region 109 interposed between the central region 107 of the waveguide 105 and the region 103 of phase change material. For example, the distance g is equal to approximately 300 nm.

[0039] The waveguide 105 is for example of the single-mode type, that is to say that it is adapted to confine and guide a single optical mode for each type of polarization. The waveguide 105 is for example more precisely adapted to confine and guide a single optical mode chosen from a zero-order transverse electric mode (TE0), parallel to the Oy axis, and a zero-order transverse magnetic mode (TM0), parallel to the Oz axis. Because the TE0 and TM0 modes are orthogonal, they cannot couple to each other in the waveguide 105. The choice of the mode confined and guided by the waveguide 105, between the TE0 mode and the TM0 mode, is determined by the polarization of the laser source LS. Thus, in a case where the laser source LS emits radiation having a transverse magnetic polarization TM, the waveguide 105 is adapted to confine and guide the zero-order transverse magnetic mode TM0 only.

[0040] On the side of its end intended to be illuminated by the laser source LS, the waveguide 105 comprises for example an input coupling element, also called the input surface of the waveguide 105. On the side of its end located opposite the region 103 made of phase-change material, the waveguide 105 may further comprise an output coupling element, also called the output surface of the waveguide 105. The input coupling element may have a structure, for example a diffraction grating having a Bragg structure or any other coupling structure, making it possible to capture the radiation emitted by the laser source LS and to propagate this radiation to the output surface.

[0041] Furthermore, the output surface of the waveguide 105 may have a structure making it possible to re-emit the radiation propagated from the input surface towards the region 103 made of phase-change material. Although this has not been detailed in FIGS. 1A and 1B, the output surface of the waveguide 105 may have a structure identical or similar to that of its input surface.

[0042] Generally speaking, the input and output surfaces of the waveguide 105 respectively make it possible, in the example shown, to receive and transmit radiation in a direction orthogonal to the direction of propagation of the radiation inside the waveguide 105, for example a direction parallel to the Oz axis. Alternatively, at least one surface, among the input and output surfaces of the waveguide 105, may have a structure allowing respectively to receive or transmit radiation in a direction parallel to the direction of propagation of the radiation inside the waveguide 105 (parallel to the Ox axis, in this example).

[0043] To switch the switch 100 from the off state to the on state, the region 103 is heated, for example, using the laser source LS, via the waveguide 105, to a temperature T1 and for a duration d1. The temperature T1 and the duration d1 are chosen so as to cause a phase change of the material of the region 103 from the amorphous phase to the crystalline phase. For example, the temperature T1 is higher than a crystallization temperature and lower than a melting temperature of the phase change material and the duration d1 is between 10 and 100 ns.

[0044] Conversely, to switch the switch 100 from the on state to the off state, the region 103 is heated, for example, using the laser source LS, via the waveguide 105, to a temperature T2, higher than the temperature T1, and for a duration d2, lower than the duration d1. The temperature T2 and the duration d2 are chosen so as to cause a phase change of the material of the region 103 from the crystalline phase to the amorphous phase. For example, the temperature T2 is higher than the melting temperature of the phase change material and the duration d2 is of the order of 10 ns.

[0045] For example, in a case where the laser source LS is based on krypton fluoride, radiation having a wavelength equal to approximately 248 nm is emitted by the laser source LS, for example in the form of pulses, to cause transitions of the material of the region 103 between the amorphous and crystalline phases. A pulse having a fluence of the order of 85 mJ.cm2 is for example used to obtain a transition of the material of the region 103 from the amorphous phase to the crystalline phase. Furthermore, another pulse having a fluence of the order of 185 mJ.cm2 is for example used to obtain a transition of the material of the region 103 from the crystalline phase to the amorphous phase.

[0046] A disadvantage of the switch 100 is that the laser radiation emitted by the source LS is not absorbed homogeneously in the region 103 made of phase-change material along the direction of propagation of the radiation in the waveguide 105 (along the axis Ox, in this example). In the example of the switch 100, the laser radiation is mainly absorbed by a first part 103N of the region 103 made of phase-change material close to the laser source LS, the absorption of the laser radiation being lower in a second part 103F of the region 103 made of phase-change material, opposite the first part 103N, further from the LS laser source than the 103N part. The optical absorption of laser radiation by the 103 region of phase change material more precisely follows a decreasing exponential from the 103N part of the 103 region to the 103F part.

[0047] Thus, during an activation phase of the switch 100, the optical power absorbed by the second part 103F of the region 103 may prove insufficient to cause a phase change of the material in the part 103F. In the case where it is desired to switch the switch 100 from the on state to the off state, this may prevent the second part 103F of the region 103 from changing phase from the crystalline phase to the amorphous phase, thus allowing, in an undesirable manner, the passage of a leakage current between the conduction electrodes 101A and 101B of the switch 100.

[0048] The inventor noticed that the phenomenon comes from the fact that the transverse magnetic mode TM of the laser signal for activating the switch 100 confined and guided by the waveguide 105 is strongly absorbed by the phase change material of the region 103, thus leading to a heating of the part 103N much greater than that observed in the part 103F. To overcome this problem, one could have thought of modifying the geometry of the waveguide 105 to confine and guide only the transverse electric mode TE, more weakly absorbed by the phase change material of the region 103 than the transverse magnetic mode TM. For example, the transverse magnetic mode TM has losses, linked to the absorption by the phase change material of the region 103, of the order of 2,500 dB.cm *, compared to approximately 500 dB.cm 1 for the transverse electric mode TE.However, for equivalent laser power values, this would not allow sufficient heating of the 103 region to cause a phase change. More generally, both in the transverse electric mode TE and in the transverse magnetic mode TM, the optical absorption follows a decreasing exponential law for this guide configuration. However, it would be preferable for the absorption to follow a linear law to allow the state of the phase change material of the 103 region to be modified.

[0049] [Fig.2A] and [Fig.2B] are schematic and partial views, respectively from above and in section along plane BB of [Fig.2A], illustrating an example of a switch 200 based on a phase change material according to one embodiment.

[0050] The switch 200 of Figures 2A and 2B comprises elements in common with the switch 100 of Figures 1A and 1B. These common elements will not be detailed again below. The switch 200 of Figures 2A and 2B differs from the switch 100 of Figures 1A and 1B in that the switch 200 comprises, instead of the guide waveform 105 located opposite the region 103 made of phase-change material, a polarization rotator 205.

[0051] The polarization rotator 205 has the function of causing a rotation of the polarization of the laser signal for activating the switch 200 above the region 103 made of phase-change material. In the example shown, the polarization rotator 205 is more particularly adapted to causing, over a distance substantially equal to a width L of the region 103 made of phase-change material, a rotation of polarization equal to approximately 90° of the laser signal for activating the switch 200. The width L of the region 103 is considered parallel to the direction of propagation of the control laser signal in the polarization rotator 205 (parallel to the axis Ox, in the example shown). In the example shown, the polarization rotator 105 is adapted to pass from the transverse electric mode to the transverse magnetic mode over a distance substantially equal to the width L of the region 103.

[0052] In this example, the polarization rotator 205 is designed so that the signal is, at the input of the polarization rotator 205, i.e. in the vicinity of the part 103N of the region 103, confined and guided exclusively in the transverse electric mode TE, weakly absorbed by the region 103, and, at the output of the polarization rotator, i.e. in the vicinity of the part 103F of the region 103, exclusively in the transverse magnetic mode TM, strongly absorbed by the region 103. This thus makes it possible to ensure that the absorption of the laser signal controlling the switch 200 is better distributed between the part 103N of the region 103 made of phase-change material, closest to the laser source LS, and the part 103F of the region 103, furthest from the laser source LS. In this example, the radiation emitted by the laser source LS has a transverse electric polarization TE.

[0053] In the example shown, the polarization rotator 205 comprises a central region 207, or core, surrounded by an electrically insulating peripheral region 209. The central region 207 and the peripheral region 209 of the polarization rotator 205 are made of materials chosen so as to obtain a contrast of optical indices making it possible to confine and guide the optical mode of interest emitted by the laser source LS. The material of the central region 207 of the polarization rotator 205 has, for example, an optical index greater than that of the peripheral region 209. For example, the central region 207 of the polarization rotator 205 is made of silicon nitride and the peripheral region 209 is made of silicon dioxide.

[0054] The plane BB of [Fig.2A] is substantially orthogonal to a direction of propagation of the laser radiation in the polarization rotator 205 (orthogonal to the axis Ox and parallel to the plane Oyz, in the example illustrated). In the example shown, the peripheral region 209 of the polarization rotator 205 covers the faces of the central region 207 parallel to the direction of propagation of the laser radiation (the faces lateral, lower and upper edges of the central region 207 of the polarization rotator 205 parallel to the axis Ox, in the orientation of FIGS. 2A and 2B). In this example, a portion of the peripheral region 209 of the polarization rotator 205 extends vertically, along the axis Oz, from a face of the central region 207 located opposite the region 103 made of phase change material (the lower face of the central region 207 of the polarization rotator 205, in the orientation of [Fig. 2B]) to a face of the region 103 made of phase change material opposite the conduction electrodes 101A and 10IB (the upper face of the region 103 made of phase change material, in the orientation of [Fig. 2B]).

[0055] In the example shown, the central region 207 of the polarization rotator 205 has, in sectional view along the plane BB, a cross-section of asymmetrical shape. More precisely, in this example, the central region 207 of the polarization rotator 205 has an L-shaped cross-section. In the orientation of [Fig.2B]: - the vertical bar of the L formed by the section of the central region 207 of the polarization rotator 205, parallel to the Oz axis, has a height hl, along the Oz axis, and a width wl, along the Oy axis; and - the horizontal bar of the L formed by the section of the central region 207 of the polarization rotator 205, parallel to the Oy axis, has a height h2, along the Oz axis, and a width w2, along the Oy axis.

[0056] In this example, the height hl is strictly greater than the height h2. Furthermore, the width wl is for example greater than or equal to the width w2.

[0057] The section of the central region 207 of the polarization rotator 205 has, for example, an invariable shape and dimensions along the axis Ox, opposite the region 103 made of phase-change material. The section of the central region 207 of the polarization rotator 205 is, for example, invariable over the entire length of the polarization rotator 205.

[0058] Furthermore, the central region 207 of the polarization rotator 205 is separated from the region 103 made of phase-change material by a distance gl. In this example, the distance gl is equivalent to a thickness of the part of the peripheral region 209 interposed between the central region 207 of the polarization rotator 205 and the region 103 made of phase-change material.

[0059] Table [Table 1] below provides examples of values ​​for the heights hl and h2, the widths wl and w2, and the distance gl as a function of the width L of the region 103 made of phase-change material along the axis Ox, i.e. perpendicular to the conduction axis Oy of the switch 200 and parallel to the direction of propagation of the laser signal in the polarization rotator 205. Two different examples are provided for the same width L of the region 103 equal to approximately 100 pm.

[0060] [Tables 1] L (pm) gl (nm) hl (nm) h2 (nm) wl (nm) w2 (nm) 100 290 450 225 400 75 100 250 250 100 150 125 80 400 250 125 210 50 65 100 1000 500 500 500 50 100 750 300 700 150 30 250 400 200 300 125 10 45 500 250 300 225

[0061] The table [Table 2] below provides, by way of example, minimum and maximum values ​​for each dimension hl, h2, wl and w2 of the central region 207 of the polarization rotator 205 and for the distance gl, the width L of the region 103 of phase change material being comprised, by way of non-limiting example, between 10 and 100 pm.

[0062] [Tables2] Dimension or distance Minimum value Maximum value gl (nm) 45 400 wl (nm) 150 700 w2 (nm) 50 500 hl (nm) 250 1 000 h2 (nm) 100 <hl

[0063] The examples provided above are however not limiting, and the person skilled in the art is capable of defining the values ​​of the dimensions hl, h2, wl and w2 of the central region 207 of the polarization rotator 205 and the value of the distance gl as a function of the width L of the region 103 made of phase-change material. Numerical simulation tools can for example be used for this purpose. For example, the distance gl and the height hl can be constrained due to the thicknesses of layers of materials deposited during manufacturing steps of the switch 200.

[0064] An advantage of the switch 200 explained above in relation to FIGS. 2A and 2B is that the presence of the polarization rotator makes it possible to ensure that the laser control signal of the switch 200 is absorbed in a substantially uniform manner by the phase change material of the region 103. More precisely, in the case of the switch 200, only the transverse electric mode TE, weakly absorbed, is present near the input of the polarization rotator 205 (in line with the part 103N of the region 103), while only the transverse magnetic mode TM, strongly absorbed, is present near the output of the polarization rotator 205 (in line with the part 103F of the region 103). This makes it possible to avoid, with respect to the switch 100 of FIGS. 1A and 1B, that a part of the region 103 made of phase-changing material, for example the part 103F furthest from the laser source LS, does not change phase when the switch is controlled.

[0065] [Fig. 3] is an isometric, schematic and partial view illustrating an example of a switch 300 based on a phase change material according to one embodiment.

[0066] The switch 300 of [Fig. 3] comprises elements in common with the switch 200 of FIGS. 2A and 2B. These common elements will not be detailed again below. The switch 300 of [Fig. 3] differs from the switch 200 of FIGS. 2A and 2B in that the switch 300 comprises a polarization rotator 305 having a variable section along the propagation axis of the laser signal (axis Ox, in the example illustrated).

[0067] The polarization rotator 305 of the switch 300 fulfills a function similar or identical to that of the polarization rotator 205 of the switch 200. In particular, the polarization rotator 305 is adapted to cause, between an input face for example located directly above the part 103N of the region 103 and an output face for example located directly above the part 103F of the region 103, a polarization rotation between the transverse electric mode TE and the transverse magnetic mode TM of the laser signal for activating the switch 300.

[0068] In the example shown, the polarization rotator 305 comprises a central region 307, for example analogous to the central region 207 of the polarization rotator 205, surrounded by an electrically insulating peripheral region, for example analogous to the peripheral region 209 of the polarization rotator 205. The peripheral region of the polarization rotator 305 has not been illustrated in [Fig.3] so as not to overload the drawing.

[0069] In the example illustrated in [Fig. 3], the central region 307 of the polarization rotator 305 comprises three parts 307A, 307B and 307C. The parts 307A and 307C of the central region 307 of the polarization rotator 305 are, in this example, located respectively opposite the parts 103N and 103F of the region 103 made of phase-change material. More precisely, in this example: - the part 307A comprises an upper zone, opposite the conduction electrodes 101A and 101B, the section of which narrows along the axis Ox in the direction of the part 307B of the region 307, and a lower zone, interposed between the upper zone of the part 307A and the region 103, of substantially constant section along of the Ox axis; - the part 307B comprises an upper zone, opposite the conduction electrodes 101A and 101B, of substantially constant section along the axis Ox, and a lower zone, interposed between the upper zone of the part 307B and the region 103, the section of which narrows along the axis Ox in the direction of the part 307C of the region 307; and - part 307C has a section widening along the Ox axis, from part 307B of region 307 towards part 103F of region 103.

[0070] This example is however not limiting, the person skilled in the art being able, from the indications of the present description, to provide that the central region 307 has a geometry different from that set out above in relation to [Fig.3].

[0071] The switch 300 has advantages identical or similar to those of the switch 200. The switch 300 makes it possible in particular, due to the presence of the polarization rotator 305, to heat the phase change material of the region 103 in a more homogeneous manner than in the case of the switch 100 previously described in relation to FIGS. 1A and 1B.

[0072] [Fig. 4] is a schematic and partial side view of an example of a transmitting array antenna 400 of the type to which, by way of example, described embodiments apply.

[0073] The antenna 400 typically comprises one or more primary sources 401 (a single source 401, in the example shown) irradiating a transmitting network 403. The source 401 may have any polarization, for example linear or circular. The network 403 comprises a plurality of elementary cells 405, for example arranged in a matrix according to rows and columns. Each cell 405 typically comprises a first antenna element 405a, located on the side of a first face of the network 403 arranged opposite the primary source 401, and a second antenna element 405b, located on the side of a second face of the network 403 opposite the first face. The second face of the network 403 is for example turned towards an emission medium of the antenna 400.

[0074] Each cell 405 is capable, in transmission, of receiving electromagnetic radiation on its first antenna element 405a and of re-emitting this radiation from its second antenna element 405b, for example by introducing a known phase shift q>. In reception, each cell 405 is capable of receiving electromagnetic radiation on its second antenna element 405b and of re-emitting this radiation from its first antenna element 405a, in the direction of the source 401, with the same phase shift q>. The radiation re-emitted by the first antenna element 405a is for example focused on the source 401.

[0075] The characteristics of the beam produced by the antenna 400, in particular its shape (or template) and its maximum emission direction (or pointing direction), depend on the values ​​of the phase shifts respectively introduced by the different cells 405 of the network 403.

[0076] Transmitting array antennas have the advantage, among other things, of being energy efficient and relatively simple, inexpensive and compact. This is due in particular to the fact that the transmitting arrays can be produced using planar technology, generally on a printed circuit.

[0077] We are more particularly interested here in antennas with a reconfigurable transmitter array 403. The transmitter array 403 is said to be reconfigurable when the elementary cells 405 are electronically controllable individually to modify their phase shift value q>, which makes it possible to dynamically modify the characteristics of the beam generated by the antenna, and in particular to modify its pointing direction without mechanically moving the antenna or a part of the antenna by means of a motorized element.

[0078] [Fig.5] is an isometric, schematic and partial view of one of the elementary cells 405 of the transmitter network 403 of the antenna 400 of [Fig.4] according to one embodiment.

[0079] In the example shown, the first antenna element 405a of the elementary cell 405 comprises a patch antenna 410 adapted to capture the electromagnetic radiation emitted by the source 401 and the second antenna element 405b comprises another patch antenna 412 adapted to emit, towards the outside of the antenna 400, a phase-shifted signal. In the example shown, the elementary cell 405 further comprises a ground plane 414 interposed between the patch antennas 410 and 412.

[0080] The antenna 410, the ground plane 414 and the antenna 412 are for example respectively formed in three successive metallization levels, superimposed and separated from each other by dielectric layers, for example made of quartz. By way of example, the ground plane 414 is separated from each of the antennas 410 and 412 by a thickness of dielectric material of the order of 200 μm.

[0081] In the example shown, a central conductive via 416 connects the antenna 410 to the antenna 412. More specifically, in the orientation of [Fig. 5], the via 416 has a lower end in contact with an upper face of the antenna 410 and an upper end in contact with a lower face of the antenna 412. The central conductive via 416 is electrically isolated from the ground plane 414. In the example shown, the ground plane 414 has a circular orifice having a diameter greater than that of the via 416, thus allowing the via 416 to pass through the ground plane 414 without the via 416 being in contact with the ground plane 414. For example, the central conductive via 416 has a diameter equal to approximately 80 μm.

[0082] In the example shown, the antenna 412 comprises a four-sided conductive plane 440. The conductive plane 440 is, for example, more precisely rectangular in shape or, as in the example illustrated in [Fig.5], substantially square in shape.

[0083] In the illustrated example, the conductive plane 440 comprises an opening 442 separating a central region 440C of the conductive plane 440 from a peripheral region 440P of the conductive plane 440. In this example, the opening 442 has a substantially annular shape, for example a rectangular or square annular shape.

[0084] In the example shown, the central conductive via 416 is in contact with the central region 440C of the conductive plane 440. More precisely, in this example, the upper end of the via 416 is connected substantially to the center of a lower face of the region 440C. The central region 440C of the conductive plane 440, delimited laterally by the annular opening 442, constitutes for example an input terminal of the antenna 412.

[0085] The antenna 412 further comprises a first switching element C1 and a second switching element C2, each connecting the central region 440C to the peripheral region 440P of the conductive plane 440. More precisely, in the example illustrated in [Fig. 5], the first and second switching elements C1 and C2 contact the peripheral region 440P in areas diametrically opposite with respect to the central conductive via 416. In this example, the switching elements C1 and C2 and the conductive via 416 are located on the same straight line parallel to one of the sides of the conductive plane 440. In this example, the switch C1 is located substantially vertically to the horizontal branch of the U formed by the slot 442.

[0086] The switching elements C1 and C2 are controlled in opposition, that is to say so that, if one of the switches C1, C2 is on, the other switch C2, C1 is blocked. This allows the second antenna element 405b of the elementary cell 405 to switch between two phase states q>, substantially equal to 0° and 180° in this example. The phase states 0° and 180° correspond respectively to the case where the switch C1 is blocked while the switch C2 is on, and to the case where the switch C1 is on while the switch C2 is blocked.

[0087] Each switching element C1, C2 of the elementary cell 405 is for example produced by one of the switches 200 and 300 described previously. In this case, using the laser source LS to control the switches C1 and C2 of the antenna element 405b has the advantage of reducing the number of electrically conductive control lines. Compared to switches made of phase-change material controlled for example by direct heating, for example by circulating a current through the phase-change material, or by indirect heating, for example by circulating a current through a heating element electrically insulated from the phase-change material, for which two control lines control lines are used, one to apply the control potential, the other to apply the reference potential, a single optical control line, for example a waveguide of a structure similar to the waveguide 105 and arranged between the laser source and the polarization rotator 205 or 305 of each switch C1, C2, is used to control the switching of each switch C1, C2.

[0088] Another advantage of the switches C1 and C2 is that they have a lower capacitance Coff in the off state than conventional indirect heating switches, which typically comprise a heating element made of an electrically conductive material, for example a metal, electrically insulated from the phase change material.

[0089] In the transmitter network 403, it is possible, for example, to use a different laser source LS to control each switch C1, C2 of each second antenna element 405b, the emission of the laser sources LS of the transmitter network 403 being controlled by a control circuit (not shown). The laser source LS is then, for example, of the “integrated” type, that is to say that it is part of the same chip as the switch(es) with which it is associated.

[0090] As a variant, it is possible to use the same laser source LS to control several switches C1, C2 of the second antenna elements 405b of the transmitter network 403. In this case, each second antenna element 405b can for example be associated with an optical switch for controlling the switches C1 and C2 in phase opposition or with a multiplexer of the “1 to N” type, with N being an integer strictly greater than two, adapted to control several switches C1, C2 of several second antenna elements 405b.

[0091] An advantage of the C1 and C2 switches based on phase change material is that they are capable of operating at power levels at least as high as the switches generally used in elementary cells of antennas with a reconfigurable transmitter or reflector array, while exhibiting better linearity. In addition, the C1 and C2 switches exhibit excellent stability in frequency ranges of the order of terahertz.

[0092] Furthermore, the transmitter network 403 comprising cells 405 integrating the switches C1 and C2 advantageously has lower energy consumption than current transmitter networks comprising, for example, components such as pin diodes or varactors.

[0093] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, the geometry and dimensions of the central regions 207 and 307 of the polarization rotators 205 and 305, respectively, may be adapted by the person skilled in the art from the indications of this description, for example depending on the intended application.

[0094] Furthermore, although an example of an elementary cell 405 comprising two switches made of phase-change material C1 and C2 has been described, the described embodiments can be transposed by a person skilled in the art to any number of switches made of phase-change material. For example, a number of switches made of phase-change material greater than two could be provided in a case where it would be desired to produce a reconfigurable elementary cell having more than two different phase states.

[0095] Furthermore, although only one example of application to transmitting array antennas has been described above, the optically controlled phase change material-based switches described in relation to FIGS. 2A, 2B and 3 may have other applications. More generally, such switches may be used in any application likely to benefit from a reduction in the number of electrical connection tracks for controlling a switch. For example, such switches may be integrated into reflector array antennas, filters, phase shifter circuits, etc. and, more generally, into any type of application using a switch.

[0096] In particular, the transposition of the embodiments described to the case of a reflector array antenna is within the reach of those skilled in the art from the indications of the present description.

[0097] Finally, the practical implementation of the embodiments and variants described is within the reach of the person skilled in the art from the functional indications given above. In particular, the embodiments described are not limited to the particular examples of materials and dimensions mentioned in the present description. Furthermore, the embodiments are not limited to the example of geometry of the patch antennas 410 and 412 described in relation to [Fig. 5], but apply more generally to any type of antenna geometry.

Claims

Claims

1. Switch (200; 300) based on a phase change material comprising: - a region (103) made of said phase change material connecting first and second conduction electrodes (101A, 101B) of the switch; and - a polarization rotator (205; 305) of a laser signal for activating the switch, located opposite a face of the region made of said phase change material.

2. Switch (200; 300) according to claim 1, wherein the polarization rotator (205; 305) comprises a central region (207; 307) of a first material surrounded by a peripheral region (209; 309) of a second material of optical index lower than that of the first material.

3. Switch (200; 300) according to claim 1 or 2, in which the polarization rotator (205; 305) is adapted to cause, between an input face and an output face, opposite the input face, a rotation of polarization of the laser signal activating the switch between a transverse electric mode and a transverse magnetic mode.

4. A switch (200) according to claim 2 or 3, wherein the central region (207) has, along a direction of propagation of the laser signal in the polarization rotator (205), an asymmetrically shaped section.

5. A switch (200) according to claim 4, wherein the section of the central region (207) is invariable over the entire length of the polarization rotator (205).

6. Switch (200) according to claim 4 or 5, wherein the section of the central region (207) has, in a plane orthogonal to the direction of propagation of the laser signal, an L shape.

7. A switch (300) according to claim 2 or 3, wherein the section of the central region (307) varies along a propagation direction of the laser signal in the polarization rotator (205).

8. A switch (200; 300) according to any one of claims 1 to 7, wherein the first and second conduction electrodes (101A, 101B) are part of an antenna element (405a) of a cell (405) of a transmitter array (403) or reflector array.

9. Cell (405) of transmitter network (403) or reflector network comprising at least one switch (200; 300) according to any one of claims 1 to 8.

10. Transmitter network (403) or reflector network comprising: - a plurality of cells (405) according to claim 9; - one or more laser sources (LS); and - a control circuit for the laser source(s).

11. Network (403) according to claim 10, in which each laser source (LS) is part of the same chip as each switch (200; 300) with which it is associated.

12. An antenna (400) comprising a transmitting array (403) or a reflecting array according to claim 10 or 11 and at least one source (401) configured to irradiate a face of the array.